1. Field of the Invention
The invention relates to fabric based body armor. More specifically, the invention relates to fabric based body armor capable of defeating multiple threats.
2. Background
In recent years, ballistic resistant materials formed from high tensile strength fibers such as aramid fabrics or polyethene fabrics have gone into common use. These fabrics have been used to form flexible fabric-based bullet defeating vests. These ballistic resistant materials typically have the advantages of greater tensile strength and less weight per unit area than metals.
High tensile strength fibers such as, for example, aramid fibers and polyethylene fibers in fabrics have been placed into vests to protect the torso of individuals. Typically, multiple layers of high tensile strength aramid or polyethene fabric are used in a single vest. Multiple layers of these materials are required because a single layer is insufficient to stop a ballistic projectile. Attaching sufficient plys of fabric to the vest necessary to defeat a ballistic projectile still leaves the vest lighter than it would be, and more flexible than had it been made out of metal.
Typically, soft fabric vests are adequate to defeat ballistic pistol rounds. One method of measuring the ability of a soft fabric vest to defeat these rounds has been established by the National Institute of Justice (NIJ). The highest level of protection standard the National Institute of Justice has issued for pistol rounds is the Level III-A Threat. The Level III-A threat is designed to simulate high velocity pistol rounds traveling at least 1,400 feet per second when they impact the target vest. The NIJ III-A Level Threat is part of the National Institute of Justice Standard 0101.04. Another part of the NIJ Standard 0101.04 is a standard for backface deformation allowed by the vest. As part of this backface deformation standard a vest, even when it stopped a ballistic projectile completely, is allowed to deform towards the body no more than 44 millimeters (mm), or 1.73 inches(in) as measured into a standard clay material.
The damage done by explosive device fragmentation can be modeled using a bullet type sabot fragment simulator. One such simulator is a right round circular penetrator. These penetrators are solid steel projectiles with blunt ends about 0.217 inches in diameter and 0.220 inches in length. Another simulator for fragmentation protection is defined by Military Standard (Mil Std) 662E. Military Standard 662E provides inter alia for a 16 grain chisel point, right round circular penetrator that impacts the vest at a velocity of at least 650 meters per second (mps) (2132 feet per second).
The principle threats faced by personnel in a military environment are ballistic projectiles and fragment/shrapnel. A military pistol ballistic projectiles is typified by a military 9 mm ball round. Fragmentation/shrapnel projectiles are typically generated by the destruction of an explosive round""s casing. The explosive round can be either artillery, mortar or grenade.
Soft fabric ballistic defeating armor vests are typically not recommended for use against fragmentation. This is because fragments, unlike bullets, do not deform as easily as bullets and are able to penetrate the multiple layers of fabric in the vest with greater ease.